We recently had a request for additional information beyond what was shown in our “Theory of Mechanical Advantage” video by Chief Instructor Dennis O'Connell. The reader would like to know more about calculating compound mechanical advantages.

First of all, a simple mechanical advantage (MA) is quite easy to calculate as long as you follow a couple of basic rules.

MAs are generally expressed in numeric ratios such as 2:1, 3:1, 4:1, etc. The second digit of the ratio, or the constant "1" represents the load weight. The first digit, or the variable 2, 3, 4, etc. represents the theoretical factor that we divide the load weight by, or inversely multiply the force we apply to the haul line.

I say theoretical as these calculations do not take into account frictional losses at the pulleys and resistance to bend as the rope wraps around the pulley tread. So a 3:1 mechanical advantage would make the weight of a 100-pound load feel like 33 pounds at the haul line, but we do lose some advantage due to those frictional losses. An even more important consideration is the fact that we multiply our hauling effort by the variable, which is important to understand when we think about the victim or an on-line rescuer that has become fouled in the structure. This is also important when considering the stresses on the haul system including the anchor, rope, and all components in the system.

We also need to pay attention to the amount of rope that must be hauled through the system to move the load a given distance. If we are using a 4:1 MA and need to move the load 25 feet, we need to pull 100 feet of rope through the system (4 X 25 feet = 100 feet).

To calculate a simple MA, remember this: if the anchor knot is at the load, it will be an odd mechanical advantage (3:1, 5:1, 7:1, etc.). If the anchor knot is at the anchor, it will be even (2:1, 4:1, 6:1, etc.) “even/anchor-odd/load.” And if you count the number of lines coming directly from the load, you will determine the variable (remember not to count the haul line if it passes one final change of direction pulley). For instance, if the knot is at the anchor and there are four lines coming from the load, this will result in a 4:1 simple MA. And if your haul line is being pulled away from the anchor, that only means you have created one final change of direction which oftentimes is done to allow the addition of a progress capture device (ratchet), or simply to make it a more convenient direction of pull. But this 5th line, called the haul line, does not come directly from the load. It comes from the final directional pulley to the haul team and is not to be counted in the simple MA ratio. We would call this set up a 4:1 MA with a change of direction (CD).

Calculating compound MAs is also quite easy. Compound MAs (sometimes called a stacked MA) simply means we are attaching a second MA to the haul line of the original MA. When we do so, we multiply the first digit of the original MA by the first digit of the second MA. If you attach a 2:1 MA to the haul line of a 4:1 MA (2 X 4 = 8), you end up with an 8:1 compound MA. Keep in mind that we have added even more frictional losses into this system, but it is still a pretty powerful MA.

There are potential benefits as well as potential penalties when using compound MAs. One benefit includes using less gear when stacking MAs. For instance, to build a simple 6:1 MA, you will require at least five pulleys, and if you want a final CD, that would require one last pulley for a total of six pulleys. If you decide to build a 6:1 compound MA, you can get away with as few as three pulleys by attaching a 2:1 MA to the haul line of a 3:1 MA. If you wanted one final CD, you would again add one more pulley for a total of four pulleys. The obvious advantage is that fewer pulleys are required, but hidden in there as another advantage is fewer pulleys for the rope to wrap which translates to less frictional loss and bend resistance.

Another benefit to stacking MAs may be the reach you need to attach to the load. If the load is 25 feet away from the anchor and you are using a 6:1 simple MA, you will need at least 150 feet of rope, plus some extra to tie the anchor knot, and some spare to wrap over the final directional - if you use one. If the load is 50 feet below the anchor and you want to stick with the simple 6:1 MA, you are looking at a minimum of 300 feet of rope.

So, what if we send a 3:1 MA down from the anchor to the load 25 feet below and attach a 2:1 to the haul line of the original 3:1 to build a 6:1 compound MA?

Well, in this case we would need 75 feet of rope plus some extra for knots for the original 3:1, and two times the length of the compounding MA throw. Throw? What the heck is throw? Throw is a term we use when we have a limited distance between the compounding MA anchor and where we can safely attach the compounding MA to the haul line of the original MA.

In the diagram below you can see the original 3:1 MA extending from its anchor to the load. The added MA, which in this case is a 2:1 has a total throw of 10 feet which requires a little over 20 feet of rope to construct. So, if we add the 75+ feet of rope required for the original 3:1 to the 20+ feet for the added 2:1, we arrive at a bit over 95 feet of rope required for this compound 6:1 MA to reach a load 25 feet from the anchor. This can be two separate ropes, one a bit over 75 feet and a second a bit over 20 feet, or it can be one rope a bit over 95 feet that we can treat as if they were two separate ropes. More on that in a bit.

Remember that we must consider the amount of rope that we need to pull through the system in order to move our load the required distance. So, using a 6:1 compound MA to move the load 25 feet we must pull a total of 150 feet of rope through the system. Whoa, wait a minute! I thought we determined that our total rope needs were only a bit over 95 feet, so how did we come up with 150 feet of rope? One of the disadvantages of compound MAs is the need for resets when the throw is not long enough to move the load the needed distance. So, even though we are using in the neighborhood of 95 feet of total rope, we are pulling the same section of rope through the second MA multiple times.

Well, this is one of the big disadvantages of a compound MA. We need to reset the system multiple times to move the load the required distance. To help envision a reset cycle, let’s assume we have our original 3:1 mounted to an anchor, and 25 feet from that anchor is the 3:1 attached to the load. The haul line of the original 3:1 goes through a final CD, and we have attached a ratchet at that final CD to capture the progress of the loads movement. One option is to find a second anchor and in this case we found one 10 feet away from the final CD of the 3:1. We tie an anchor knot and attach it to that second anchor and route the remaining 20+ feet of rope through a pulley which we attach to the haul line of the original 3:1 with a rope grab. We now have our 2:1 pulling on the haul line of a 3:1 resulting in a 6:1 compound MA.  But…… and there’s always a “but,” isn’t there? We can only move the load a bit over 3 feet at a time before we completely collapse the 2:1 and need to reset it for the next haul. Remember, the 2:1 only has a 10-foot travel or “throw” and that distance is divided by 3 as it is pulling on a 3:1 MA. In addition to that, we have pulled about 20 feet of rope through the 2:1 just to move the load a bit over 3 feet. In order to move the load the entire 25 feet we will need to reset the system about 8 times and that is some slow going. Just to point out one option to speed up the haul by reducing the amount of resets needed, if you sent the original MA to the victim as a 2:1 and then stacked a 3:1 MA with 10 feet of throw onto that 2:1, you would still have your compound 6:1 but would only need to do about 5 resets and could do it with a bit over 80 feet of rope.

There are all sorts of options when deciding what type and ratio of MA to use in a rescue effort. You can get pretty creative when building MAs, but be aware that creativity can sometimes lead to crazy. Remember the KISS principle…keep it simple and safe.

If you are overbuilding an MA just to show a cooler way of doing it, you may be missing the point of the job. There is someone in trouble that is relying on you getting them up and out of their predicament, and sometimes we can get a little carried away with our creativity, especially when it comes to MAs. 3:1 Z-rigs are a great option especially with the addition of devices like the Petzl ID or the CMC MPD as your first MA change of direction and progress capture device. Plus, this gives you the ability to convert to a lower with friction control already built in. But you can really complicate things by compounding a second MA onto a Z-rig to get a higher ratio MA. You will soon learn that now you have to perform two separate resets of the haul cams. And, if you are out of sequence in the reset, the haul cam of the second MA will jam into the traveling pulley of that system and stop you in your tracks. There are some tricks to really make the resets for this system go nicely, but that will have to wait for another day.

There are hundreds of variations that you can use for compounding MAs, but once again I caution you to remember KISS. I have my favorites and every once in a while the situation calls for something a little different, and that’s where understanding the advantages and disadvantages of the systems is of great value.

For additional video resources on mechanical advantage as well as other techniques and systems, visit Roco Resources.

On Oct. 21, 2016, a D&D Construction employee entered a drainage shaft to clean out mud and debris. No personal fall protection was utilized as the worker descended via bucket 10 ft. into the shaft, which was 4.5 ft. in diameter and lined with concrete.

At some point, the worker lost consciousness due to the oxygen deficient atmosphere in the confined space and fell 40 ft., then drowned in a foot of water.

“Cal/OSHA launched a confined space educational program to bring attention to the dangers and preventable deaths that occur in confined spaces,” said Cal/OSHA Chief Juliann Sum in a statement. “The program helps employers identify hazards and create effective safety plans that include air monitoring, rescue procedures and training before work begins.”

General contractor Tyler Development was constructing a single-family residence in the Bel Air area and hired subcontracted D&D Construction to install and service reinforced concrete posts known as caissons on the property, according to the agency’s report.

The state-run occupational safety unit cited Tyler Development and D&D Construction Specialties Inc. a combined $352,570 for ten serious and willful health and safety violations following an investigation. Cal/OSHA said neither company was in compliance with required confined space procedures.

D&D Construction previously was cited in 2012 for similar safety violations at a different job site.

In total, D&D has to pay a proposed $337,700 for 13 violations, including two willful serious accident-related, one willful serious, one serious accident-related, six serious, and three general in nature.

According to Cal/OSHA, the company failed to:
• ensure safe entry into the confined space
• have an effective method to rescue the worker in the confined space in an emergency
• test the environment to determine if additional protective equipment, such as a respirator or oxygen tank, were required to work safely in the shaft.

Tyler Development was cited $14,870 for five violations, three of them serious, for a failure to:
• evaluate the worksite for possible permit-required confined spaces
• ensure that the subcontractor meets all requirements to comply with a permit space program
• protect workers from the hazard of impalement by guarding all exposed reinforced steel ends that extend up to six feet above the work surface with protective covers

A full copy of the report is available here.

The following article was written by Russell Warn and published in ISHN magazine (ishn.com), December 2016. Roco comments have been added to the article and are noted in red.

Working in confined spaces presents a unique and dangerous challenge in combatting the unseen – oxygen deficiency, poisonous or explosive gases, and other hazardous substances are among the most frequent causes of accidents associated with work in confined spaces and containers.

From 2005-2009, the Bureau of Labor Statistics reported nearly two deaths per week, or roughly 96 per year, could be attributed to confined space, with about 61 percent occurring during construction repair or cleaning activities.

With conditions subject to change in a moment’s notice, taking steps to protect against life-threatening dangers should always be a top priority in confined spaces. Performing a thorough clearance measurement is a demanding — yet crucial — task that dictates the safety environment, and should not be taken lightly. To help guide you along your road to enhanced safety, outlined below are several best practices based on frequently asked questions.

When should I perform a clearance measurement?

Conduct clearance measurements immediately before operations begin. Environmental factors such as temperature and air flow can change the atmosphere, causing readings to fluctuate. One shift’s measurement taken at 7 a.m. is not representative of the conditions when work operations commence for another shift at 4 p.m. New clearance measurements must be taken immediately to account for the nine hours of changing temperatures and ventilation patterns, depicting the accurate readings of present conditions.

Roco Comment: In addition to pre-entry clearance measurements, entry into permit spaces during construction activities requires "continuous atmospheric monitoring" unless the entry employer can demonstrate that equipment for continuous monitoring is not commercially available or periodic monitoring is sufficient. Ref. 1926.1203 (e)(2)(vi), 1926.1204 (e)1)(ii), and 1926.1204 (e)(2). Additionally, Roco believes that for "ALL" permit entry operations, it is advisable to provide continuous atmospheric monitoring no matter what the industry activity entails.

What’s the importance of zero-point adjustment?

When performing clearance measurements, it’s crucial to determine the reference point of the gas detector by calibrating the zero-point. The zero-point ensures that the indicated values correspond to the actual existing gas concentrations. In order to determine that the actual zero-point has been found, calibrate equipment in an environment where the hazardous substance is not present, such as fresh air environments. With every scientific test, no matter the field, a control group, which serves as a starting point of reference, permits for the comparison of results to show any contrasting changes. The zero-point calibration acts as such, allowing workers to identify the presence, or lack thereof, of different gas concentrations.

Where do I measure/take the sample?

When it comes to measuring samples, there are four things to keep in mind: the physical properties of gases, and the type and shape, temperature and ventilation patterns of the confined space.

Know the differences between light and heavy gases. Clearance measurement experts must have a strong working knowledge of hazardous substances’ properties, as they play a role in where measurements should be taken. For example, if a sample is pulled from the top of the confined space and hydrogen sulfide (H2S) is detected, the sample may not be entirely reliable. H2S has a molar mass of 34 g/mol, which is significantly heavier than that of air (29 g/mol). As a result, H2S sinks to the bottom of a space, where its concentration would be greatest. Identifying a presence at the top of the confined space says immediate danger and appropriate actions should be taken.

Light gases quickly mix with air and rise to the top. As a result, any measurements in open atmospheres should be performed close to the leak, and increases in concentration should appear in the highest points of the confined space. Heavy gases, on the other hand, should sink and flow like liquids, pass obstacles or stick to them. They barely mix with air like light gases do, so their samples should always be taken at the lowest points of the confined space.

Determine the type/shape of the confined space: In an ideal scenario, each confined space area would be in an “even” or level position. This isn’t always the case, and a container may be placed on an inclined surface, making the highest point in the corner positioned toward the top of the inclined surface. Thus, entry may be nearer to where the heavy gases have accumulated.

Take tabs on temperatures. All matter is made up of atoms and molecules that are constantly moving. When heat is added to a substance, such as a gas, the molecules and atoms vibrate faster. As the gas molecules begin to move faster, the speed of diffusion increases. If the sun has been shining on a tank for hours, there’s a good chance the clearance measurement taken at dawn no longer reflects the current readings due to the increase in diffusion.

Vet the ventilation. Air currents change the position and concentration of air clouds, and often times, the way a confined space is ventilated can affect readings. Containers cannot always be separated from pipelines, or there may be leaks in the tanks that must be accounted.

Roco Comment: Not only is it required by certain OSHA provisions like alternate entry procedures, but Roco highly recommends monitoring the atmosphere prior to initiating ventilation. This is intended to provide a reasonable assessment of the potential atmosphere change should the ventilation equipment fail. The rate for a potential hazard to re-develop will be based on factors such as the effectiveness of isolation, any residual product within the space, temperature, humidity and passive ventilation which are among just some of the factors.

How do I safely conduct the measurement for an accurate reading?

People often question why they can’t just use the carrying strap of their device to lower the device into the confined space for a reading. Although this seems like a simple fix, it’s not a safe or recommended way to conduct the measurement. Lowering the device into the container this way not only obscures the way the display is read, but it may not audibly alarm. If the measured value is slightly below the threshold value and the alarm does not sound, a worker would not be notified of the dangerous concentrations lurking below. Not only this, but measurements may be inaccurate since the measured gases, due to their molar masses, may be concentrated at a higher or lower point within the container. Clearance measurements should be conducted on-site and on-the-ground of the confined space for accurate, safe readings.

Roco Comment: The points made in the preceding paragraph are certainly valid. The best solution that we can offer is to use remote sampling probes or tubes to actively draw (pump) samples from the stratified levels of the space while the direct reading instrument is in a position outside the space to observe the real time readings. To expound upon the point the author makes, if the pre-set threshold for the alarms are not enough to trigger the alarm indicating the presence of a hazardous atmosphere, and the individual performing the assessment relies instead on rapidly pulling the monitor from the space in the hope that they are able to read the display before the values change, is a very dangerous way of approaching this procedure. Depending on the sampling rate of the monitor, the hazardous gas(s) may have cleared from the monitor in the time it takes to withdraw it from the space, and it is very likely that the instrument will display a normal atmosphere by the time it is back within view. Additionally, for areas within the space that cannot be remotely assessed by remote sampling prior to entry, the only safe recourse is to limit entry to the areas that have been assessed and to take a monitor into the space to continuously assess the unreachable regions before venturing further.

What do I need to document during clearance measurement protocols?

Just as it’s important to remain thorough in clearance measurements procedures, it’s equally as important to remain thorough in the general housekeeping protocols surrounding samples. This includes documenting:

• • The container number
• • The measuring point of the container, and whether there was more than one measuring point
• • At which time was the clearance performed
• • Under what condition was the measurement performed
• • Measured hazardous substances
• • Name of person performing measurement
• • Equipment used for clearance

Safety, regardless of job title or responsibility, should be everyone’s top priority. When working in the midst of poisonous and explosive hazards, performing clearance measurements correctly and carefully means not only keeping one’s self safe, but keeping the working environment safe, as well.

About the Author:
Russell Warn is the product support manager for gas detection products at Dräger. He has been in the safety industry for more than 29 years, with most of this time dedicated to gas detection product and application support.

As shown in this photo, an engulfment scenario was featured at last year's Rescue Challenge. Be aware...it only takes 5 seconds for flowing grain (or other product) to engulf and trap a worker.

In 60 seconds, the worker is submerged and is in serious danger of death by suffocation. More than half of all workers engulfed die this way. Many others suffer permanent disability.

OSHA has recently issued further warnings on the dangers of working in grain or bulk storage facilities.

An "engulfment" often happens when "bridged" grain and vertical piles of stored grain collapse unexpectedly. Engulfments may occur when employees work on or near the pile or when bin augers whirl causing the grain to buckle and fall onto the worker. The density, weight and unpredictable behavior of flowing grains make it nearly impossible for workers to rescue themselves without help.

"Far too many preventable incidents continue to occur in the grain-handling industry," said Kim Stille, OSHA's regional administrator in Kansas City. "Every employee working in the grain industry must be trained on grain-handling hazards and given the tools to ensure they do not enter a bin or silo without required safety equipment. They must also take all necessary precautions - this includes using lifelines, testing the atmosphere inside a bin and turning off and locking out all powered equipment to prevent restarting before entering grain storage structures."

In 2016, OSHA has opened investigations of the following grain industry fatalities and incidents:

• March 16, 2016: A 42-year-old superintendent at Cooperative Producers Inc.'s Hayland grain-handling site in Prosser, Nebraska, suffered fatal injuries caused by an operating auger as he drew grain from a bin. OSHA cited the company on Sept. 9, 2016, for three egregious willful and three serious violations and placed the company in its Severe Violator Enforcement Program. The company has contested those citations. See news release here.
• March 22, 2016: A 21-year-old worker found himself trapped in a soybean bin, but escaped serious injury at The Farmer's Cooperative Association in Conway Springs, Kansas. Rescue crews were able to remove the worker and he was treated and released at a local hospital. On June 2, 2016, OSHA cited the company for 13 serious violations.
• March 25, 2016: A 51-year-old employee was trapped in a grain bin at McPherson County Feeders in Marquette, Kansas. Emergency crews were able to rescue him. OSHA cited the company for four serious violations on April 14, 2016.
• May 19, 2016: A 53-year-old male employee at Prinz Grain and Feed suffered severe injuries on May 18, 2016, as he worked in a grain bin in West Point, Nebraska. The maintenance worker was in a grain bin when a wall of corn product collapsed and engulfed him. He died of his injuries two days later.
• Sept. 1, 2016: A 59-year-old employee suffered severe injuries to his leg when the sweep auger inside a bin at Trotter Grain in Litchfield, Nebraska, caught his coveralls.
• Sept. 19, 2016: A 28-year-old employee of the Ellsworth Co-Op in Ellsworth, Kansas, had his left leg amputated when he stepped into an open auger well inside a grain bin while the auger was running.

"It is vital that we work with leaders, farmers and those employed in the grain and feed industry to increase awareness of hazards in the grain industry and discuss ways to protect workers on the job," stated an Omaha OSHA official.

We add that it’s critically important for emergency responders to be aware of the dangers they may face in bulk storage facilities. In addition to engulfment, there’s also the risk of dust explosions as well as entrapment from moving mechanical equipment.

Does a competent person inspect your rescue equipment each year?

If not, you may want to consider having an independent third party perform the inspection for you. This service is offered by Roco as a stand-alone service, or it can be added to your next private training session. 

Functional Ops Check

The service includes a “sight and touch” functional inspection of hardware, nylon products (including rope, webbing, and anchoring components), harnesses, and accessory equipment (including litters and stretchers) utilized in confined space/high angle applications. The inspection will be conducted in accordance with manufacturer’s specifications and will satisfy the requirement for an annual² inspection by a competent person.
Note: Equipment recommendations will NOT be provided by inspection personnel unless requested to do so.

Service Inspection Benefits include:

• Certified personnel to inspect equipment to manufacturer's standards.
• Inspection documentation from an independent third party.
• Frees your personnel from the responsibility of equipment inspections.

A full report of findings will be provided to include accessibility of equipment to responders and any other recommendations to improve overall team performance. It will include other pertinent information such as the manufacturer, product number, and serial/lot number (where applicable), date of manufacture, and in-service date (when available). It will also include the results of pass/fail testing for both visual and functional inspection. All equipment deemed unsuitable for use will be tagged for removal from service.

Regardless of the stated service life, the condition of equipment – as determined through inspection by a qualified party – is a key factor in determining whether or not a piece of equipment is fit for service.

Although the definition of “equipment lifespan” is very broad depending on the manufacturer, each provides specific instructions on proper inspection of equipment and detailed explanations on when to retire the service item. Several general identifiers that pertain to all equipment are shown below.

Reasons for Equipment Retirement include:

• Item fails to pass any pre/post use or competent person inspection.
• Item has been subjected to a major fall or load.
• Item is constructed of plastic or textile material and is older than 10 years.
• You cannot determine the complete full-use history of item.
• You are not certain or have lost confidence in the equipment.

As a reminder, it is very important to keep the manufacturer’s instructions when purchasing new equipment. This is vital to identifying and keeping track of the manufacture date as well as other important information. For example, if the manufacture date of equipment, such as life safety rope and harnesses, cannot be identified; it can pose extreme liability for agencies or facilities whose teams may potentially be operating with equipment that has passed its service life. It could also create a compromise in the safe operation of the equipment.

A 10-year service life for nylon/polyester products is set according to ASTM F1740-96 (American Society for Testing and Materials).

Inspect Rescue Equipment Every Time It’s Used

All team members should be qualified and knowledgeable enough to perform pre- and post-use inspections of equipment. It is crucial that all members document each use of equipment, denote any deficiencies, and report to the proper person. One person should be designated to perform the competent person annual inspection. This person should have complete knowledge of the equipment and inspection procedures as well as the authority to keep or remove equipment from service as they see fit. If team members are unable to fill this role, a qualified third party with applicable manufacturer certifications in competent person inspection should be utilized to assist in determining the condition and estimated service life of rescue equipment.

Download Roco's Quick Checklist for your convenience. →

Rescue team members are encouraged to attend this inspection where they will receive information on proper pre- and post-use inspections for their equipment. Guidance can be also offered in areas of equipment care, inspection, record-keeping, and proper storage. Again, equipment recommendations will not be addressed unless specifically asked to do so – this is only an inspection of the equipment you currently have on site.

Remember, with rescue gear, lives are literally “on the line,” – if in doubt, throw it out!

To schedule your Roco Competent Person Inspection, or add it to your current training dates, call us at 800-647-7626 or email info@rocorescue.com. Roco offers this service at no charge for current customers or for a very nominal fee for non-customers.¹

¹ Current customers receive a one-day equipment inspection at no charge. Travel expenses apply for out-of-town customers.

² References include: 1926.502 Appendix C; ANSI Z359.2 Section 5.5.2 Inspections; ASTM Rope Inspection Guide; NFPA 1983 Section 5.2; ANSI Z359.11 Annex A (harnesses); and ANSI Z359.4 Section 6.1.

NOTICE: The client remains responsible for ensuring that all guidelines and requirements for maintaining and, where indicated, removal of equipment from service, are followed. This includes removing equipment from service anytime there is a situation or incident that occurs during handling, training, or rescue, that might have caused damage or otherwise compromised the integrity of the equipment, particularly where internal damage that is not visible might be present (e.g. equipment dropped from height, exposure of nylon products to chemicals or other potentially degrading substances, etc.). Client will be required to complete a certification that between Roco inspections, the equipment was properly stored, was available only to personnel trained to use the equipment properly, and that any equipment that was exposed to any condition or occurrence that could have resulted in hidden damage has been removed from service. A company representative, preferably someone from the rescue team, must be present during the inspection process.